Any translating apart from what's done now is beyond the scope of this extension. It is only meant as a very simple addition to provide this sometimes painfully missing feature. So sorry, but the translation of posts will have to be done by another extension

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Just to emphasize how simple the code is:
If you dig into the code you will see it's less code then you'd expect, just because it heavily relies on existing functionality. There are only 129 lines of code, most of which is standard phpBB stuff. Not counting those lines, it would probably add up to about 20 lines of unique code. (11 lines in the listener, 9 lines in the template and 1 line language.)